The Detroit Lions, like the rest of the NFL, had to act quickly in free agency during the lockout-shortened offseason.

ALLEN PARK, Mich. — The Detroit Lions, like the rest of the NFL, had to act quickly in free agency during the lockout-shortened offseason.

They made the most of their limited window by signing veterans Stephen Tulloch and Justin Durant, both of whom have turned one of the team's weaknesses into an asset. Detroit also kept DeAndre Levy and Bobby Carpenter after parting with Julian Peterson and Larry Foote, decisions that look good so far.

"Our linebacker corps obviously is much improved," Lions coach Jim Schwartz said. "It's not just the quality of the players, it's the depth that we have, too, for the inevitable situations that occur when you have guys that fall."

Like in the last game.

Detroit (4-0) didn't have Durant on the field for its comeback win against the Dallas Cowboys because of a concussion and might not have him back to play the Chicago Bears (2-2) on Monday night. Durant sounded hopeful earlier in the week he would be cleared to hit after an evaluation Tuesday, but was relegated to watching the parts of Wednesday's practice that were open for the media.

If Durant can't go, Carpenter showed he can make plays in his place.

The former first-round pick, one of any acquisitions that have panned out for general manager Martin Mayhew, made his first career interception and touchdown against his former team Sunday to start a 24-point comeback.

"We didn't have Durant and not only did you not notice that he wasn't out there, but you noticed Bobby Carpenter," Schwartz said.

The linebacking corps has quietly and consistently made plays on a defense usually recognized for its front led by Ndamukong Suh and Kyle Vanden Bosch.

Tulloch, who got a day of rest Wednesday, leads the Lions with 26 tackles this season. He had 160 tackles last year for Tennessee — 53 more than any other Titan — a season after making a team-high 120 stops. But the three-year starter didn't feel wanted as a free agent by the franchise that made him a fourth-round pick in 2006 out of North Carolina State, so he figured it was time to go.

"I gave the organization everything I had for five years, but they didn't offer me what I felt I deserved even after I became a leader and captain," Tulloch said, sounding more matter of fact than bitter. "When free agency opened up, coach Schwartz, who was in Tennessee when I got drafted, gave me a chance to come up here with a one-year deal in a scheme I know to let me earn what I think I deserve."

Tulloch has done for Detroit what he's always done, sprinting from sideline from sideline to deliver blows on ballcarriers.

The son of a single mom who gave her time and money when both were scarce is making an impact on and off the field in Detroit as well just as he did in Tennessee and South Florida.

He has partnered with former NBA and Michigan standout Jalen Rose at his charter school, asking students to write essays about leadership, with a chance to be among the 55 children he hosts each game; plans to help 55 kids from a facility that aids homeless kids to get their teeth cleaned this month; and has invited 80 breast cancer survivors Monday night to line the tunnel before kicking off against Chicago.

"When you're an NFL player with resources to do anything you want, I don't think it's right to not give back," Tulloch said. "My mom motivates me to always do more because when she raised me, my brother and sister in Miami by herself, she gave back even when she didn't have anything but time and love to give, and that rubbed off on me."